1. Field of the Invention
The present invention relates to an electronic watch mounted with a microcomputer, and particularly to a multifunctional electronic watch in which consumed electric power is cut down.
2. Description of the Prior Art
Conventionally, an electronic watch mounted with a microcomputer determines if various conditions for the operation of moving hands such as if a stem of the watch is wound or not, and if the watch is in a time display mode or not are satisfied in every operation of moving hands. In order to make these determinations, a flag confirmation is conducted and a corresponding process is executed when the flag matches with a branch condition. Subsequently, a confirmation is conducted on the next flag condition in the next branch and if the electronic watch is multifunctional, these operations were repeated a number of times.
As an electronic watch becomes more multifunctional, the number of times to make a determination and to branch increases, and the number of times to confirm a flag increases. Further, when the operation of moving hands is conducted every second, the above operations are also conducted every second.
However, a conventional electronic watch mounted with a microcomputer confirms whether the flags match with the various branch conditions before performing the operation of moving hands, and executes. Because of this, the operation before the moving of hands becomes longer leading to a problem in that as an electronic watch becomes more multifunctional, the operations of the above takes a longer time. As a result, a period of time during which a CPU is operative becomes longer, an operating electric current of a CPU increases, and there is more consumed electric current of an IC. For instance, a current is approximately 5.0 mA at an operating time of the CPU while it is 0.5 mA at a stand by time. In an electronic watch, a hand is normally moved once per second. Thus the longer operating time of the CPU causes the life of a battery of a watch to be shortened.
In order to solve the foregoing problem, an electronic watch according to the present invention comprises an oscillation circuit; a system clock generating circuit for generating a system clock from the output of the oscillation circuit; a frequency dividing circuit for dividing the output of the oscillation circuit; a ROM in which processing procedures such as chronological operations of a watch are programmed; a CPU for reading the data programmed in the ROM and for performing various arithmetic operations; an interrupt signal generating circuit for generating an interrupt signal to the CPU; a RAM for storing various kinds of data; and a flag management circuit for determining the state of a flag that becomes a branch condition during an arithmetic operation performed by the CPU.
In this structure, when the CPU reads data programmed in the ROM to perform various arithmetic operations, the CPU recognizes the state of a flag in the flag management circuit before performing an arithmetic operation. Therefore, when it is not necessary to perform a determination branch operation other than the movement of hands during the arithmetic operation, the operation of moving hands can be carried out without having to sequentially determine the branch conditions. A portion of the determination branch operation can be collectively determined such that the operation of moving hands can be carried out without having to make a sequential determination on all the branch conditions. Further, by providing a switch means, when it is not necessary to use the flag management circuit, it can be used as a general register to enhance the storage capacity and the operational ability of an arithmetic operation.